In recent years, liquid crystal display devices having a function for stereoscopically displaying an image (hereinafter also referred to as “displaying a 3D (stereo) image”) in addition to a function for two-dimensionally displaying an image (hereinafter also referred to as “displaying a 2D (flat) image”) have been developed.
Technologies for displaying a stereo image, such as an active shutter system, a lenticular system, and a patterned retarder system (or a polarization system, also called a PR system) are known. In any of the systems, presenting a right-eye image only to the right eye of a user and a left-eye image only to the left eye of the user allows the user to visually perceive an image in stereo.
In a liquid crystal display device that employs the active shutter system, left-eye frames (L frames) and right-eye frames (R frames) are alternately displayed. A user observes an image displayed on the liquid crystal display device with 3D glasses, thereby being able to visually perceive the image in stereo. The 3D glasses have a lens for the left eye and a lens for the right eye which provide shutter operations in synchronization with the switching between the L frames and the R frames.
A liquid crystal display device that employs the lenticular system presents a left-eye image and a right-eye image individually to the left eye and the right eye of a user through a lenticular lens formed on the front side of a liquid crystal panel. This allows the user to visually perceive the image in stereo without using 3D glasses.
In a liquid crystal display device that uses a patterned retarder, for example, a right-eye image is displayed using pixels selected through odd-numbered horizontal scanning lines, and a left-eye image is displayed using images selected through even-numbered horizontal scanning lines.
In the following, the patterned retarder system will be more specifically described with reference to FIGS. 34 to 36. FIG. 34 is an exploded perspective view illustrating a backlight unit 50, a liquid crystal panel 60, and a patterned retarder 70, which are included in a liquid crystal display device of the related art that uses a patterned retarder.
The backlight unit 50 emits light to the liquid crystal panel 60 from the back of the liquid crystal panel 60. The liquid crystal panel 60 has formed thereon pixels delimited by horizontal scanning lines (lateral scanning lines) HL1 to HLN (N is the total number of horizontal scanning lines) and vertical signal lines (longitudinal signal lines) VL1 to VLM (M is the total number of vertical signal lines).
In the liquid crystal panel 60, it is possible to control the transmittance of light on a pixel-by-pixel basis by controlling the alignment of liquid crystals in each pixel. In the liquid crystal panel 60, furthermore, a right-eye image is displayed using pixels selected through odd-numbered horizontal scanning lines HL1, HL3, and so forth (hereinafter referred to as odd-numbered pixels), and a left-eye image is displayed using pixels selected through even-numbered horizontal scanning lines HL2, HL4, and so forth (hereinafter referred to as even-numbered pixels).
The patterned retarder 70 is a retarder having a longitudinal direction which is the horizontal scanning line direction, and is composed of two kinds of retarders RR and RL having different characteristics. The retarders RR are configured to convert linearly polarized light into right-handed circularly polarized light, and the retarders RL are configured to convert linearly polarized light into left-handed circularly polarized light.
As illustrated in FIG. 34, the retarders RR, which are shaped into bands whose longitudinal directions are parallel to the horizontal scanning lines, are disposed on the front side of the odd-numbered pixels arranged along the horizontal scanning lines HL1, HL3, and so forth, and, similarly, the retarders RL, which are shaped into bands whose longitudinal directions are parallel to the horizontal scanning lines, are disposed on the front side of the even-numbered pixels arranged along the horizontal scanning lines HL2, HL4, and so forth.
Accordingly, a right-eye image displayed using the odd-numbered pixels is represented by light which is transmitted through the patterned retarder 70 and is then right-handed circularly polarized, and a left-eye image displayed using the even-numbered pixels is represented by light which is transmitted through the patterned retarder 70 and is then left-handed circularly polarized.
FIG. 35 illustrates 3D glasses 80 used in the patterned retarder system. As illustrated in FIG. 35, the 3D glasses 80 include a lens for the right eye and a lens for the left eye. The lens for the right eye transmits only right-handed circularly polarized light, and the lens for the left eye transmits only left-handed circularly polarized light. With the use of the 3D glasses 80, the user is able to observe, in an image displayed on a liquid crystal display device, a right-eye image displayed using the pixels delimited by the odd-numbered horizontal scanning lines (hereinafter referred to as odd-numbered pixel rows), only with the right eye, and a left-eye image displayed using the pixels delimited by the even-numbered horizontal scanning lines (hereinafter referred to as even-numbered pixel rows), only with the left eye. This provides the user with a visual perception of the right-eye image and the left-eye image with parallax as a stereo image.
A liquid crystal display device of the patterned retarder system is also capable of normally displaying a 2D image having no parallax by using both the odd-numbered pixel rows and the even-numbered pixel rows. In this case, the user may simply observe an image displayed on the liquid crystal display device without using 3D glasses.
The 3D glasses 80, which are used in the patterned retarder system, do not require any electrical control, unlike 3D glasses used in the active shutter system, and can therefore be implemented with a simple configuration.
On the other hand, it is known that the patterned retarder system suffers from a phenomenon called crosstalk mainly due to the finite thickness of a glass layer forming a liquid crystal panel.
The crosstalk, as used herein, is a phenomenon in which a right-eye image is mixed into a left-eye image visually perceived by the user or, similarly, a left-eye image is mixed into a right-eye image visually perceived by the user. For example, when the user observes the liquid crystal panel from obliquely above, part of a right-eye image displayed using the odd-numbered pixel rows is observed after passing through the retarders for the left eye, which are disposed on the front side of the even-numbered pixel rows. Thus, the right-eye image is mixed into a left-eye image. Also when the user observes the liquid crystal panel from obliquely below, part of a left-eye image displayed using the even-numbered pixel rows is observed after passing through the retarders for the right eye, which are disposed on the front side of the odd-numbered pixel rows. Thus, the left-eye image is mixed into a right-eye image.
Hitherto, a configuration in which crosstalk, described above, is suppressed by forming black matrices and black stripes on a liquid crystal panel and a patterned retarder, respectively, along the horizontal scanning lines has been known.
FIG. 36 is a schematic partial cross-sectional view of the backlight unit 50, the liquid crystal panel 60, and the patterned retarder 70, which are included in a liquid crystal display device of the related art, taken along the vertical signal line direction (longitudinal direction). In FIG. 36, the configuration around the pixels Pn delimited by the n-th horizontal scanning line and the pixels Pn+1 delimited by the (n+1)-th horizontal scanning line is illustrated. In FIG. 36, the liquid crystal panel 60 and the patterned retarder 70, which are configured such that crosstalk is suppressed by the black matrices BM and the black stripes BS, are illustrated.
As illustrated in FIG. 36, the liquid crystal panel 60 includes a first polarizing plate 60a, a glass substrate 60b, a TFT array 60c, a color filter 60d, a CF glass substrate 60e, a second polarizing plate 60f, and a liquid crystal layer 60g disposed between the TFT array 60c and the color filter 60d. 
On the TFT array 60c, circuit-forming elements such as horizontal scanning lines and TFTs are formed between the pixels Pn and the pixels Pn+1. Furthermore, on the front side of the circuit-forming elements, the black matrices BM are formed in the color filter 60d, and the black stripes BS are formed in the patterned retarder 70.
Such black matrices and black stripes as described above can suppress the occurrence of crosstalk when the angle defined between the direction normal to the liquid crystal panel 60 and the direction of the line of sight is within ±α degrees in the vertical signal line direction.
However, this configuration has a problem in that, in addition to a reduction in the luminance of a 2D image and a 3D image due to the use of the patterned retarder 70, a further reduction in luminance due to a reduction in aperture ratio caused by black matrices and black stripes occurs.
In NPL 1 given below, there is proposed a technology for suppressing crosstalk by dividing each pixel into two sub-pixels (an upper sub-pixel and a lower sub-pixel) in the vertical signal line direction, without providing the patterned retarder 70 with black stripes BS. In this technology, when a 2D image is to be displayed, a data voltage used for image display is supplied to both types of sub-pixels, and when a 3D image is to be displayed, a data voltage used for image display is supplied only to the upper sub-pixels and a data voltage used for black display is supplied to the lower sub-pixels. The lower sub-pixels to which the data voltage used for black display is supplied function as black matrices which are large in width.
According to the technology disclosed in NPL 1, therefore, the black stripes BS in the patterned retarder 70 can be omitted, resulting in no reduction in image luminance when a 2D image is displayed. In addition, when a 3D image is to be displayed, the lower sub-pixels function as black matrices and therefore the occurrence of crosstalk can be suppressed.